Laminated carpet fabrics comprising a carpet and a secondary backing fabric affixed to the carpet by an adhesive are known in the art. Numerous adhesives and methods of applying adhesive to fabrics for the purpose of laminating adhesively coated fabrics to other pieces of fabric are also well known.
Typically, an adhesive is applied to a carpet to bond the tufts to the primary backing and to bond the carpet with a secondary backing material to form a laminated structure. After application of the adhesive, the carpet and secondary backing are brought into intimate contact with each other and then are passed between a pair of laminating rollers. The laminating rollers are configured to cause adhesive on the back of the carpet to be transferred from the carpet to the secondary backing and also to maintain the materials in intimate contact. The laminated structure is then typically treated by suitable means to solidify the adhesive.
The quality of the bond between the carpet and secondary backing and the amount of adhesive required are in part determined by the method chosen for applying the adhesive. Various methods are known to the art and fall into two categories. The first category comprises methods which apply the adhesive to the carpet and transfer it from the carpet to the secondary backing. These methods are wasteful of adhesive, since the valleys and depressions in the back surface of the carpet must be substantially full to transfer sufficient adhesive to the secondary backing.
The secondary category comprises methods for applying adhesive directly to the secondary backing. One method in this category comprises dipping the secondary backing directly into the adhesive, which is again wasteful because it coats surfaces which do not contact the carpet. Another method comprises applying the adhesive to the secondary backing from an adhesive-coated roller. The adhesive is formed into a layer on a rotating casting roller, and the backing fabric being conveyed in the opposite direction to the rotating casting roller is brought into contact with a portion of the casting roller to transfer the adhesive from the casting roller onto the backing fabric. However, as the backing fabric is drawn away from the casting roller, the fabric is dragged through the oncoming layer of adhesive on the casting roller, smearing the adhesive on the fabric backing and causing an uneven coating. Additionally, the high viscosity of the adhesive on the casting roller tends to pull at the adhesive transferred onto the backing fabric, causing some of the adhesive to be pulled off of the fabric backing, or causing additional adhesive to be pulled off the casting roller and onto the backing fabric. Thus, this coated roller method tends to produce a coating on the secondary backing which is so unevenly deposited that an excessive amount of adhesive must be applied to assure adequate lamination strength.
These methods of lamination require the application of relatively large amounts of adhesive to achieve the desired delamination strength of the bond between the carpet and the secondary backing. Such systems are shown in U.S. Pat. Nos. 2,428,358, 3,238,595, 3,567,548, and 3,669,779.
Accordingly, there is a need to provide a method for applying a uniform coating of adhesive to only the surfaces of the secondary backing which are to come in contact with the carpet, while avoiding the coating of non-contacting surfaces and use of excessive adhesive. Further, there is a need to reduce the amount of wasted adhesive while maintaining laminated carpet structures which provide acceptable delamination strength between the carpet and the secondary backing fabric. Prior art processes have not heretofore been able to accomplish these goals with acceptable results.